Range and Endurance Calculation of Propeller Aircraft Based on Linear Relationship between Engine Fuel Flow Rate with Shaft Power

For turboprop, piston-propeller, and tiltrotor aircraft, the fuel flow rate generally has a linear relationship with the shaft power. For the case where the constant term of such linear relationship is not zero, the calculation methods for the long-range and long-endurance performance of above aircrafts flying at equal altitudes were derived which include the optimal flight speed, lift coefficient, range, and endurance. A simulation calculation of endurance performance was conducted using a high-speed rotary wing aircraft and a piston-propeller business aircraft as examples. The results indicate that the longest-range flight mode of this type of aircraft is a variable attitude and variable speed mode, but during the cruise phase its lift coefficient changes very little. If the lift coefficient and cruising speed of the flight mode of longest-range at half fuel weight are taken as the lift coefficient values of the flight mode with constant attitude, as well as the speed values of the flight mode with constant speed, respectively, then the latter two flight modes have almost the equal range values with the ones of long-range flight mode. For the flight requirements of long endurance, the longest-endurance flight mode takes the flight parameters of constant attitude and variable speed. However, if the optimal speed of the longest-endurance flight mode at half fuel weight is taken as the speed value of the flight mode of constant speed and variable attitude, the latter can obtain almost equal endurance with the former.